When Hurricane Sandy hit the NYC metro area, talking heads described how you had to view your vehicles as lifeboats - get your bug-out gear and leave. It was impractical to remain in some areas without power or gasoline as the temperatures dropped in the following weeks. The idea of remaining in a city, where too many people are fighting over too few resources, simply isn’t practical; after Katrina, people started trickling out into the streets as their supplies ran out.
We were fine without power for a few days, because the temperature was OK and we had supplies. The most useless thing was the radio; it just told us how crappy it was elsewhere...
How were the roads out of Sandy’s path? I expect they will be totally gridlocked in any real SHTF.